Semiconductor devices of optical neural network and methods of forming the same

Abstract

A semiconductor device includes an oxide layer having a first side and a second side opposite to each other. The semiconductor device includes a plurality of first waveguides that are disposed across a plurality of first insulator layers, respectively, on the first side of the oxide layer. The semiconductor device includes a plurality of second waveguides that are disposed across a plurality of second insulator layers, respectively, on the second side of the oxide layer. The plurality of first waveguides and the plurality of second waveguides collectively form a plurality of photonic neural network layers of an artificial neural network.

What is claimed is: 
     
         1 . A semiconductor device, comprising:
 an oxide layer having a first side and a second side opposite to each other;   an input optical device formed on the first side of the oxide layer;   an output optical device also formed on the first side of the oxide layer;   a plurality of first waveguides that are disposed across a plurality of first insulator layers, respectively, on the first side of the oxide layer; and   a plurality of second waveguides that are disposed across a plurality of second insulator layers, respectively, on the second side of the oxide layer;   wherein the plurality of first waveguides and the plurality of second waveguides collectively form a plurality of photonic neural network layers of an artificial neural network.   
     
     
         2 . The semiconductor device of  claim 1 , wherein the plurality of first waveguides and the plurality of second waveguides are each formed of silicon nitride. 
     
     
         3 . The semiconductor device of  claim 1 , wherein the plurality of first waveguides and the plurality of second waveguides are each formed of silicon. 
     
     
         4 . The semiconductor device of  claim 1 , further comprising:
 a first interconnect structure extending through the plurality of first insulator layers and electrically coupled to the input optical device; and   a second interconnect structure extending through the plurality of first insulator layers and electrically coupled to the output optical device.   
     
     
         5 . The semiconductor device of  claim 1 , wherein the input optical device is configured to receive a first array of optical signals, at least some of the plurality of first waveguides and the plurality of second waveguides are configured to perform a liner transformation and then a nonlinear transformation on the first array of optical signals into a second array of optical signals, and the output optical device is configured to convert the second array of optical signals into a plurality of electrical signals. 
     
     
         6 . The semiconductor device of  claim 1 , wherein the input optical device and the output optical device are both formed below a bottommost one of the plurality of first insulator layers. 
     
     
         7 . The semiconductor device of  claim 1 , wherein the plurality of first waveguides and the plurality of second waveguides each have a tapered end, when viewed from the top. 
     
     
         8 . The semiconductor device of  claim 7 , wherein adjacent ones of the plurality of first waveguides have their respective tapered ends vertically overlapped with each other, and adjacent ones of the plurality of second waveguides have their respective tapered ends vertically overlapped with each other. 
     
     
         9 . The semiconductor device of  claim 1 , wherein a respective subset of the plurality of first waveguides disposed in each of the plurality of first insulator layers collectively function as a first one of the plurality of photonic neural network layers, and a respective subset of the plurality of second waveguides disposed in each of the plurality of second insulator layers collectively function as a second one of the plurality of photonic neural network layers. 
     
     
         10 . An apparatus for implementing an artificial neural network, comprising:
 an input region configured to receive a first optical signal;   a neural network region optically coupled to the input region and configured to transform the first optical signal to a second optical signal; and   an output region optically coupled to the neural network region and configured to convert the second optical signal into a first electrical signal;   wherein the neural network region comprises a plurality of waveguides that are disposed across a plurality of vertically stacked insulator layers, respectively.   
     
     
         11 . The apparatus of  claim 10 , wherein the input region includes at least one modulator configured to modulate the first optical signal based on a second electrical signal received through a first via structure. 
     
     
         12 . The apparatus of  claim 10 , wherein the input region includes at least one photodetector configured to output the first electrical signal through a second via structure. 
     
     
         13 . The apparatus of  claim 10 , wherein the plurality of waveguides are each formed of silicon nitride. 
     
     
         14 . The apparatus of  claim 10 , wherein the plurality of waveguides are each formed of silicon. 
     
     
         15 . The apparatus of  claim 10 , wherein the plurality of insulator layers are each formed of silicon dioxide. 
     
     
         16 . The apparatus of  claim 10 , wherein the plurality of waveguides collectively form at least one of a sequence of layers of an artificial neural network. 
     
     
         17 . A method for making semiconductor devices, comprising:
 forming a plurality of optical devices in an overlaying silicon layer disposed on a first side of a silicon-on-insulator (SOI) substrate;   forming, over the plurality of optical devices, a plurality of first waveguides disposed across a plurality of first insulator layers, respectively;   attaching a carrier substrate to the SOI substrate with the plurality of first waveguides interposed therebetween;   flipping the SOI substrate;   removing an underlying silicon layer disposed on the second side of the SOI substrate to forming the plurality of second waveguides;   forming, over a second side of the SOI substrate opposite to the first side, a plurality of second waveguides disposed across a plurality of second insulator layers, respectively; and   forming a plurality of interconnect structures electrically coupled to the plurality of optical devices, respectively;   wherein the plurality of first waveguides and the plurality of second waveguides collectively form a plurality of photonic neural network layers of an artificial neural network.   
     
     
         18 . The method of  claim 17 , wherein the plurality of first waveguides and the plurality of second waveguides are each formed of silicon nitride, silicon, or combinations thereof. 
     
     
         19 . The method of  claim 17 , wherein the plurality of first waveguides are each formed of silicon nitride. 
     
     
         20 . The method of  claim 17 , wherein the plurality of first waveguides are each formed of silicon.